Connecting devices that operate without prestripping are known in the prior art in the form of a connecting device constituted of a flat spring, cut in a U or fork shape, the branches of which are elastically biased one against the other and provided with sharp edges and which define a slot into which is introduced the insulated wire which is to be connected, as indicated in the description of the German Utility Design No. 70 30 836.
In this device, the insulated wire to be connected is introduced at the end of the slot adjacent the free ends of the branches of the connecting device where the insulated sheath is perforated. The wire is then forced toward the other end of the slot where it is tightly held by the resilient branches.
This type of connecting device has a disadvantage inherent to its own structure, since the perforation of the insulation is made at the end of the branches, which is the portion where the deformation of the branches is the easiest, thereby requiring a strong restoring force in order that the cut in the insulating sheath can be effectively realized. Besides, the tightening of the core of the electric wire, after having been bared, is effected nearer to the common portion of the branches of the connecting organ, i.e., at a spot where the deformability of the branches is the smallest and where, consequently, these branches can damage the core of the wire if the restoring force of the branches is too strong, or can form a poor electrical, mechanical, and thermal contact in the opposite case.
In order to improve the qualities of the elasticity of the branches at the point of contact with the core of the wire to be connected, it is necessary to increase the total length of the branches and to provide at the proximity of their bases a wider recess than that of the slot for cutting the insulating material and the squeezing of the core of the conducting wire.
In order to facilitate the placement of insulated wire in this type of connecting device, the connecting blocks have been improved as described in the U.S. Pat. No. 3,936,128. In this connector, the connecting device of the above described type is mounted in the cover of a box, while the box comprises two parallel bores destined to receive the wires which are to be connected. The connection of the wires is obtained by introducing them into the respective bores of the box and placing the cover on the box.
By introducing the wires into the connecting device through the portion of the slot formed by the free end of the branches, means must be provided in the box for assuring a precise guiding of the wires and to correctly position their axes relative to the slot.
Such connector blocks present barriers to miniaturization, and the connectors require the use of different connecting devices according to the diameter of the wires to be connected, which naturally limits the flexibility of using this device and prohibits the use of a standard connecting device for two wires of a different diameter. Besides, if the wires to be connected comprise a core formed of multiple strands, a certain number of these strands cannot be correctly urged into the slot between the free ends of the branches of the connecting device, and the strands obstruct the engagement of the cover and do not make proper electrical contact.